The CAS Registry Mumber 81498-20-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,4,9 and 8 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 81498-20: (7*8)+(6*1)+(5*4)+(4*9)+(3*8)+(2*2)+(1*0)=146 146 % 10 = 6 So 81498-20-6 is a valid CAS Registry Number.